Floating body silicon-on-insulator (SOI) transistors are limited in operating voltage and power due to accumulated hot carriers which can increase the electrical potential of the body region of the SOI transistors. Body tied SOI transistors have been shown to extend voltage and power handling capabilities when compared to floating body SOI transistors.
Floating body SOI transistors have shown non-conducting hot carrier drift (e.g. magnitude of threshold voltage to decrease and the drain current to increase when in the non-conducting state) for drain to source voltage (Vds) larger than about 3.2 volts. Body tied devices have been shown to not suffer from this mechanism.
When a floating body transistor is conducting, a corresponding floating body effect can cause abrupt reduction of output impedance of the transistor under moderate bias at various levels of drain to source voltage of the transistor, which in turn can reduce analog gain of the transistor and increase complexity of a corresponding device modeling. Body tied devices (transistors) suppress the reduction of the output impedance and extend the range of higher output impedance to higher drain to source voltages.
Body ties on wide (large gate width) transistors with conventional (H-gate, T-gate) body tie structures become less effective in suppressing device degradations due to high resistance and increased parasitic capacitance which mitigate the ability to control the floating body effects. In particular, conventional body tied devices (e.g. H-gate, T-gate) are less effective in suppressing such degradations for large transistor width and the added drain to gate capacitance associated with conventional body tied devices can degrade performance in applications where such transistors are used, such as, for example, radio frequency (RF) amplifier applications.
Although body ties can improve transistor voltage capability, the on state conduction performance of the transistor can be degraded.